Morphology transition control of polyaniline from nanotubes to nanospheres in a soft template method

A soft template route is reported for the fabrication of polyaniline nanospheres via the oxidative polymerization of aniline in the presence of -naphthalenesulfonic acid (-NSA) as both surfactqant and dopant, and ammonium persulfate as oxidant at 2-5 degrees C. Control over the morphology and size of the nanoparticles was achieved by changing the reaction medium via addition of an organic cosolvent (i.e. ethanol or ethylene glycol) and by controlling the concentrations of aniline and -NSA and the molar ratio of -NSA to aniline. By this means the size of the -NSA-aniline micelles and the way that aniline monomer interacts with the micelles were controlled. In fact the lower dielectric constant of organic cosolvent, due to reduction of the possibility of dissociation of ionic species, causes the monomer to exist mostly as neutral aniline molecules rather than as anilinium cations. The neutral aniline molecules form aniline-filled micelles with -NSA, which act as soft templates for the formation of polyaniline nanospheres. Scanning and transmission electron microscopies, dynamic light scattering, and Fourier transform infrared and UV-visible spectroscopies were used to characterize the products. The mechanism of morphology transition from nanotubes to nanoparticles is discussed based on the experimental observations. (c) 2014 Society of Chemical Industry